Put the spinach in a large colander
and pour over boiling water. Once cool
enough to handle, squeeze out any
excess water, then season.
Tip the tomatoes into a frying pan with
some seasoning and simmer for 5 mins
to thicken. Add the fish and heat for
1-2 mins – it doesn’t need to be fully
cooked at this point. Stir in the basil.
Heat oven to 220C/200C fan/gas 7.
Divide the spinach, fish, prawns and
tomato sauce between 2 gratin dishes.
Mix the Parmesan, breadcrumbs and
oats together and sprinkle over the top.
Bake for 20 mins until golden and
bubbling. Serve with cooked broccoli.